Virtual machine environments have been increasingly developed with recent improvement in hardware performance and improvement in virtualization techniques. Flexibility of environment structures for virtualization has been increased as well to be able to assume various forms according to a request.
On the other hand, in a virtual machine environment, virtualization invites an increase in the amount of the processing to degrade access performance as compared with that in a physical environment. In order to mitigate such effect and improve the performance, techniques have been developed of executing more direct access.
Related art of the present invention is disclosed in Patent Literature 1 to Patent Literature 4.
Patent Literature 1 recites that fiber-channel (FC) frames directing a predetermined destination are all transferred to the predetermined destination. Patent Literature 2 recites that after switching an I/O device assigned to a guest OS of a shifting source to a physical computer on a shifting destination, a virtual computer and a guest OS on the shifting destination are activated to complete migration. Patent Literature 3 recites that a data center to which a migration request is to be sent is determined based on data center information. Patent Literature 4 recites that a differential memory image is transmitted to a migration destination virtual server.
Patent Literature 1: Japanese Patent Laying-Open No. 2011-134296
Patent Literature 2: Japanese Patent Laying-Open No. 2010-039685
Patent Literature 3: Japanese Patent Laying-Open No. 2009-134687
Patent Literature 4: Japanese Patent Laying-Open No. 2009-140053
Environment in which direct access is executed, however, causes a problem. The problem is difficulty in changing a physical environment. Since one of the advantages of virtualization systems is enabling flexible change of a virtualization environment without being affected by a physical environment, it is a crucial issue to ensure flexibility. Performance and flexibility are said to have a trade-off relation under these circumstances. Technique for enabling coexistence of performance and flexibility in a virtualization environment is accordingly demanded.
In a system using virtual machine (VM) and a Fiber-Channel Storage Area Network (FC-SAN), for example, it is a structure of a method of directly showing a disk to a VM (pass-through) that exhibits I/O performance of a storage disk most. Structure that shows a disk by pass-through has a problem that no migration is possible with a VM in operation.